Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$223.65	11.822%	$250.0899	$250.09	$250.10	$250.10
Purchase #2	$99.35	3.128%	$102.4577	$102.46	$102.45	$102.50
Purchase #3	$56.36	6.381%	$59.9563	$59.96	$59.95	$60.00
Purchase #4	$95.73	4.853%	$100.3758	$100.38	$100.40	$100.40
Purchase #5	$114.28	8.260%	$123.7195	$123.72	$123.70	$123.70
Purchase #6	$45.31	7.343%	$48.6371	$48.64	$48.65	$48.60
Purchase #7	$150.61	6.648%	$160.6226	$160.62	$160.60	$160.60
7 purchase totals =	$785.29		$845.8589	$845.87	$845.85	$845.90